Mineralogy and geochemistry of clinopyroxene in peridotites of Nehbandan ophiolitic complex, eastern Iran

The petrographical examination of peridotites of the Nehbandan ophiolitic complex revealed that the peridotites of Kalateh Shahpouri, Qadamgah, Lah-Kouh, Cheshmeh anjir, Bandan, and Zolfaghari were of harzburgite type and Sefid-Kouh and Nasfandeh-Kouh were of lherzolite type. Generally, the types of clinopyroxenes in the peridotites of this complex were diopside. The geochemical investigation of clinopyroxenes in Mg# vs. Al2O3, Cr2O3, and TiO2 graphs and Ti vs. Nd, Zr, and Sr graphs shows that the peridotites of Nasfandeh-Kouh, Bandan, Zolfaghari, and Sefid-Kouh with a low degree of partial melting belong to the Abyssal tectonic setting and back-arc basin.on the other side, the harzburgites of Kalateh Shahpouri and Cheshmeh anjir were formed in the Supra-subduction zone tectonic setting and fore-arc basin and have a high degree of partial melting. The study of incompatible elements, LILE and HFSE in spider diagrams normalized to the primary mantle and as well as the study of REEs in spider diagrams normalized to the chondrite for clinopyroxenes confirm this issue. Therefore, Nasfandeh-Kouh and Sefid-Kouh lherzolites as well as Qadamgah, Lah-Kouh, Bandan, and Zolfaghari harzburgites with a low degree of depletion were more consistent with the Mid-oceanic ridgestectonic setting, and the harzburgites of Kalateh Shahpouri and Cheshmeh anjir were close to the Supra-subduction zone tectonic setting with a high degree of depletion.